In this paper, a grid connected microgrid with multiple inverter-based distributed generators (DGs) is considered. DG in FFC mode regulates the microgrid as a controllable load from the utility point of view as long as its output is within the capacity limit. The transition mode causes a change in frequency of microgrid due to the loss of power transferred between main grid and microgrid. Frequency deviation from the nominal value can exceed the limit if the loss of power is large enough. This paper presents a coordinated control method for inverter-based DGs so that the microgrid is always regulated as a constant load from the utility viewpoint during grid connected mode, and the frequency deviation in the transition mode is minimized. DGs can share the load by changing their control modes between UPC and FFC and stabilize microgrid during transition.

Demand Response and Ancillary Service Management Using Fractional-Order Integral Indicator and Dynamic Game Model for an Aggregator Program in Smart Grids, Technology and Economics of Smart Grids and Sustainable Energy, 2016, 1, 1

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Power Scheduling of Distributed Generators for Economic and Stable Operation of a Microgrid, IEEE Transactions on Smart Grid, 2013, 4, 1, 398